The India Meteorological Department (IMD) has recently reported cold wave conditions over Delhi. This report sheds light on the various components of cold waves, the areas of India majorly affected, specific situations in Delhi, and potential reasons for the decreasing temperature in the region.
Understanding Cold Waves
A cold wave is defined as a rapid decrease in temperature within 24 hours, reaching a point that demands significantly more protection for agriculture, industry, commerce, and social activities. For plains, a cold wave is announced when the minimum temperature lowers to 10 degrees Celsius or below and is 4.5 degrees Celsius less than the standard for two consecutive days. Coastal stations, however, rarely experience a minimum temperature of 10 degrees Celsius. Nonetheless, locals may feel discomfort due to the wind chill factor, which can reduce the minimum temperature by several degrees depending on the wind speed. The wind chill factor measures the cooling effect that wind has on air temperature.
India’s ‘Core Cold Wave Zone’
India’s ‘core cold wave zone’ includes areas like Punjab, Himachal Pradesh, Uttarakhand, Delhi, Haryana, Rajasthan, Uttar Pradesh, Gujarat, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, West Bengal, Odisha and Telangana. In 2019, Delhi and the surrounding northern areas experienced their coldest winter of the century.
Current Cold Wave Situation in Delhi
On the 3rd of November, 2020, Delhi recorded a minimum temperature of 10 degrees Celsius, which was 5 degrees Celsius below normal. If this temperature persists for another day, IMD may declare a cold wave.
Possible Causes for the Fall in Minimum Temperature
The most probable reasons for the present drop in minimum temperature across the region include an absence of cloud cover, snowfall in the upper Himalayas leading to the blowing of cold winds towards the region, and subsidence of cold air over the region. Subsidence refers to the movement of cold and dry air downwards closer to the surface. Weak La Nina conditions currently prevalent in the Pacific Ocean could also contribute to the fall in temperature. La Nina corresponds to unusually cooler sea surface temperatures along the equatorial Pacific Ocean and is linked to intense cold waves. During La Nina years, both the severity of cold conditions and the area under cold wave grip increase.
Winter 2020 Predictions
The upcoming month of November is predicted to be colder than usual as the mean minimum temperature for October 2020 was recorded at a low of 17.2 degrees Celsius. This marks the lowest since 1962 when the recorded temperature was 16.9 degrees Celsius.
About India Meteorological Department (IMD)
Established in 1875, IMD is an agency under the Ministry of Earth Sciences of the Government of India. It is the primary body in charge of meteorological observations, weather forecasting, and seismology.
